private void OnOldPasswordMaskedChanged(Catel.Data.AdvancedPropertyChangedEventArgs args)
        {
            var oldValue = args.OldValue as string;
            var newValue = args.NewValue as string;

            if (((oldValue ?? string.Empty).Length + 1) == ((newValue ?? string.Empty).Length))
            {
                var change = (newValue ?? string.Empty).Substring((oldValue ?? string.Empty).Length, 1);
                OldPassword      += change;
                OldPasswordMasked = OldPasswordMasked.Replace(change, "*");
            }
            else if ((oldValue ?? string.Empty).Length > (newValue ?? string.Empty).Length)
            {
                OldPassword       = OldPassword.Substring(0, (newValue ?? string.Empty).Length);
                OldPasswordMasked = OldPasswordMasked.Substring(0, (newValue ?? string.Empty).Length);
            }
        }